Aggregation-induced emission (AIE) has already been applied for in-situ monitoring living radical polymerization process. Here we utilized functionalized monomer TPEE as fluoresce probes for the in-situ monitoring of photo-induced RAFT-PISA process. Hydrophilic POEGA macro chain transfer agent (Macro-CTA) was first prepared with light sensitive CTA 4-Cyanopentanoic acid dithiobenzoate, and (2-(4-vinylphenyl)ethene-1,1,2-triyl)tribenzene (TPEE) was copolymerized with styrene to form the hydrophobic block under UV irradiation. The growth of hydrophobic block induced the self-assembly of polymer chains and the emission signal could be observed by naked eyes afterwards. The PL intensity increased with the increase of particle size, as well as the monomer conversion and molecular weight, owing to the enhancement of AIE monomer in the self-assembly latex particles. This no-invasive and facile approach to in-situ visualization and continuously monitoring of the photo-induced RAFT-PISA process might be helpful for both scientific research and commercial application.
RAFT-mediated polymerization-induced self-assembly (RAFT-PISA) has been undergoing fast development currently, promoting research toward more diverse morphologies and more cutting-edge applications. Herein, we demonstrate a polymerization-pH tailored RAFT-PISA (pH-PISA) process, which can conveniently harvest abundant nano/micro-scale morphologies using popular monomers N,N-dimethylacrylamide (DMAA) and diacetone acrylamide (DAAM). The process proceeded through ordinary RAFT dispersion polymerization in an aqueous medium but under different pH conditions. With the use of pH-sensitive bi-carboxylic acid-capped trithiocarbonate as the chain transfer agent (CTA), it was found that the PISA of propagating amphiphilic ABA triblock copolymers was highly affected by the different ionization of the CTA. When the polymerization pH was adjusted to 2.5, an especially wide spectrum of morphologies was detected, including spheres, worms, lamellae, single or double-head tadpoles, vesicle strings and large spheres with surface protrusions. However, the diversity in morphology gradually declined when the polymerization pH was increased to 6 or 8. Diverse structures with same monomer compositions provide an ideal model to explore the influence of particle morphology on ice recrystallization inhibition (IRI) activities. The variations in mean largest grain sizes (MLGS) and growth rates of a single ice crystal were related to packing parameters (P), bridging the interface geometry of the packing of amphiphilic molecules and ice-controlling activities.
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